The Zoeller pump organization states that a stuck float switch is one of the main causes of pump failure. What happens is the switch may be stuck in the low-level position, which allows the pump to keep running when dry. Since it is a submersible pump, it relies on the fluid for cooling and lubrication of the impeller and pump mechanisms. Running the pump when dry will eventually burn out the bearings.
If the intake is allowed to clog, no lubricating fluid enters the pump section. The motor still spins, and the pump bearings will eventually burn out due to dry running. To prevent this, check the intake from time to time to clear any clogging that may occur. Special filters may be obtained or designed, which will allow fluid in, but keep clogging material out.
Lack of Maintenance
The pump does need regular maintenance. Every year, clean and check the impeller and pump internals. Clean the impeller assembly thoroughly to remove debris such as small rocks or sticks. Zoeller pump organization recommends checking the outlet pipe often for clogging issues, since a clog creates undue back pressure. This can strain the motor, reducing its lifespan.